My mouth, Heb. my palate, which being one of the instruments of speech, is put for another, or for all the rest. The sense is, If any secret passion or desire of his hurt did arise in me, I forthwith suppressed it, and did not suffer it to grow and break forth into an imprecation of hurt to him.
Related Commentaries of Job 31:30
Job 31:30
30 Neither have I suffered my mouthf to sin by wishing a curse to his soul.